1. Field of the Invention
The present invention relates to a connecting structure which electrically connects a connecting terminal provided on a substrate and a connector provided on an electronic device by a bump formed of an anisotropic conductive paste, a method for forming a bump by an anisotropic conductive paste, and a method for producing a device-mounting substrate which joins a substrate and an electronic device by a bump formed of an anisotropic conductive paste.
2. Description of the Related Art
For example, as a technique to mount an LSI chip on a substrate, connecting a connecting terminal on the LSI chip and a connecting terminal on the substrate via a solder ball is mostly common. However, since the solder is hard material, distortion may be generated in a connecting portion thereof due to concentration of stress when the aforementioned technique is applied to a substrate having large surface irregularities, a substrate having poor positioning accuracy of connecting terminals, or a hard substrate such as ceramic substrate. Further, in a long term, there is possibility that stress crack may be generated in solder due to residual stress.
To solve such problems, as a technique to realize alleviation of stress at low cost, there is proposed a connecting structure using an anisotropic conductive film (ACF) (for example, Japanese Patent Applications Laid-open Nos. 2002-43363, 2002-261416). This anisotropic conductive film is made by dispersing conductive material particles in a binder formed of resin and making this binder to a film form, in which, when being compressed by applying a constant load, the particles of the conductive material contact each other to thereby have a conductivity in a compressive direction. In a connecting structure using such an anisotropic conductive film, the resin as a soft material relaxes the stress, and thus a crack is not easily generated as compared to the case where connecting portions are formed only with solder as in a conventional technique.